Protective compositions



Patented Jan. 23, 1945 PRQTECTIIVIE (DQMPGSKTION S .lolm Cc Lum, Union, anu lll'uomas .l. Keeling, Bloomfield, N. 3., assiguors to Westinghouse Electric 8.; Manufacturing 'Company,

East

fittsburgh, its, a corporation of Pennsylvania No Drawing.

Application @cto'ber 2 1, 1942,

Serial No. 46324.6

(El. iot -173) 5 Claims.

invention relates to protective composithat may be applied to surfaces of metals e like to provide for protection of the une; surfaces from chemical reagents.

he treatment of metals and other sub- .ces with various r agents to produce particusui'fece conditions, it is frequently necessary stop-oli or prevent the action of the reagents 11 certain surface portions of members. Fro ently, treating sheets of metal with acids, es, and other substances to produce a pre iiuecl surface condition, portions of the ust be shielded from the action of such .cs the like in order to maintain the 1 condition of the metal. treatment, it is ordinarily necessary cve the stop-oil or protective composition d surfaces to which such composition was The requirements for a satisfactory pic e stop-oil composition are that the composile easily applied easily removed without cg substantial damage to the surfaces being etc-cl. essential requirement is that the tion protect the underlying surfaces res of th reagent or the temperature of the he metal is subjected. 1

us invention is to provide a proicomposition which when applied resists the action of acids, alkalies other inorganic chemicals and which c applied. in the molten state to surface members to protect such areas from the or cold inorganic chemicals. objects of the invention will in part be us and will in part appear hereinafter. ccordine' to this invention, the highly desirprotective composition is prepared by comng ethyl cellulose and cetyl acetamiole. The l acetamicle which has been employed is obiable to the trade under the trade-name rawax i7. Other sources for the cetyl acetamlcle are available. Acetamides of aliphatic hyairocalroons having other than 17 carbon atoms; 50:. example aliphatic acetamides of from 12 to 24 carbon atoms may be equally successful in some cases.

satisfactory protective composition has been produced by combining from 1 to 80 parts of ethyl cellulose with 99 to 20 parts by weight, of cetyi aoetamicle. The most consistent results have been obtained by a composition of approximately ethyl cellulose and 90% cetyl acetprotective stop-off composition. which amide. The method of combining the two components is to heat the cetyl acetamide to the melting point of around 135 C. and add the ethyl cellulose in powder form. When the mixture has been completely melted, it may be applied to surfaces it is desired to protect. As the proportion oi ethyl cellulose is increased, the melting point of the composition increases somewhat. More important though the viscosity of the molten mixture increases considerably with the proportion of ethyl cellulose. A composition of 20% cctyl acetamide and ethyl cellulose is so viscous that it is somewhat diificult to apply to members. Another advantage in favor or" the composition having the lower proportions of ethyl cellulose is that the melting point of the mixis below the point at which ethyl cellulose begins to char. In using other acetamides, such clodecyl to carnaubyl acetamide, similar proportions with ethyl cellulose may be used.

:1 some cases, it may be cles'uable to add small a1 cunts or" gums and resins to the mixture in order to reduce the cost or modify the properties of molten composition such as viscosity. A w percent of Congo gum or Batu resin may be to replace a part of the ethyl cellulose. Polystyrene may be added in the amounts of up to 5% A small percentage of cellulose acetate may also be introduced into the composition.

lilcpal, shellac and vinyl chloride polymers may be added with some advantage. l'he limitation upon the amount of these third components that may be added resides in the lack of compatibility of any large amount of sum or resin with the cetyl acetamide. For most additions less than 10% is the limit of compatibility. Within this limitation it may be advantageous to replace a portion of the ethyl cellulose with the gums or resins to produce changes in viscosity, hardness of the coatings and cost.

The molten composition may be applied to surfaces of members which it is desired to protect by anyone of several methods. Sheets of metal may be dipped if the portions to be protected will be covered by the dipping operation. In other cases, a mask may be applied to the'metal surfaces, and on brushing or dipping the hot composition will coat the portions of the surfaces presented through the mask. The member whose surfaces have been coated with the composition will be generally so much cooler than the composition that the film of composition will con geal almost immediately and form a tenacious adherent waxy coating. The coatin will not be further treated. Members protected with the boiling solution of calcium sulphate and calcium oxide in water for fifteen minutes. After the aluminum strip has passed through this sequence of operations, the strip is dipped into a benzene solvent. The benzene solvent causes the coatin to swell and loosen from the surfaces of the aluminum strip. The coating then can be peeled oflf the metal as a substantially unitary strip without leaving any adherent particles of composition behind. I

It will be apparent that the composition may be applied extremely rapidly to members, and

'sinceno time is necessary in order to dry the coating or to remove solvents, members so treated maybe processed at once. The coating may be treated in hot or cold inorganic reagent of all types without causing the coating to peel or crack or otherwise fail. In order'to remove the coating, a dip in a solvent causes the coating to swell and loosen to such an extent that the coating may be stripped without any difliculty. It will accordingly be apparent that the composition introduces significant economies into the selective treatment of surfaces of metals and the like.

Since certain changes can be made in the above invention and different embodiments of the invention can be made without departing from the scope thereof, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting. sense.

We claim as our invention:

1. A protective stop composition for application to surfaces in the molten state as a. coating comprising 20% to 99% by weight of an acetamidc of an aliphatic hydrocarbon of from 12 to 24 carbon atoms and a major proportion of the remainder comprising ethyl cellulose, the coating resistant to the action of acids, alkalies and many organic chemicals.

2. A protective stop composition for application to surfaces in the molten state as a coatin comprising 20% to 99% by weight of cetyl acetamide and a major proportion of the remainder comprising ethyl cellulose and a minor proportion of resins and natural gums, melting-at about 135 C. and compatible with the cetyl acetamide, the coating resistant to the action of acids, alkalies and many organic chemicals.

3. A protective stop composition for application to surfaces in the molten state as a coating comprising from 99% to 20% by weight of cetyl acetamide and from 1% to by weight of ethyl cellulose, the coating resistant to the action of acids, alkalies and many organic chemicals.

4. A composition suitable for application as a melted coating to surfaces of metal and the like, the hardened coating being inert to the action of hot or cold acids, alkalies and many inorganic chemicals without blistering or peeling, the composition comprising 99 to 20 parts by weight of cetyl acetamide and 1 to 80 parts by weight of ethyl cellulose.

5. A composition suitable for application as a melted coating to surfaces of metal and the like, the hardened coating being inert to the action of hot or cold acids, alkalies and many inorganic chemicals without blistering or peeling, the composition comprising 99 to 20 parts by weight of cetyl acetamide and 1 to 80 parts by weight of ethyl cellulose, and a natural gum or resin in an amount equal to 10% and less of the cetyl acetamide, the gum or resin melting at about C. and compatible with cetyl acetamide. JOHN CJ'LUM. Thomas J. KEA'I'ING. 

